This application relates generally to gas turbine engine rotor assemblies and, more particularly, to bearing assemblies for gas turbine engine rotor assemblies.
Gas turbine engines typically includes a fan rotor assembly, a compressor, and a turbine. The fan rotor assembly includes a fan including an array of fan blades extending radially outward from a rotor shaft. The rotor shaft transfers power and rotary motion from the turbine to the compressor and the fan, and is supported longitudinally with a plurality of bearing assemblies. Bearing assemblies support the rotor shaft and typically include rolling elements located within an inner race and an outer race.
Additionally, at least some known bearing assemblies include a plurality of identical springs attached to the bearing outer race. The springs are spaced equally in a single row circumferentially around the rotor shaft to provide a discrete radial stiffness to the bearing and to center the outer race with respect to the support frame. A first end of the springs is attached to the bearing assembly outer race, and a second end of the springs is attached to a flange coupled to a support frame.
During operation, an unbalance within the engine may cause the engine rotor shaft to displace radially. The radial displacements of the shaft are transmitted to the bearing assembly. Because the springs are arranged in a single circumferential row, the deflection of each spring is the same. A parallel or dual row configuration facilitates optimizing the weight of the bearing assembly by utilizing a shorter axial space. However, this configuration also reduces the spring bending stresses, thus increasing fatigue life. In this stress field, a generic single row configuration would require more springs, a greater material strength, greater cross-sectional inertia, and/or an increased spring length. As a result, a cost and weight of the bearing assembly would increase.
To minimize the effects of potentially damaging radial forces, the number of springs, the cross-sectional area, and the length of the springs are often increased. As a result, the cost and weight of the bearing assembly is also increased.